ON DISTINCTION BETWEEN ALLOY SOFTENING DUE TO NITROGEN AND NICKEL IN DILUTE LATTICE SOLUTION IN IRON

Alloy softening is observed in both FeN and FeNi in tensile tests conducted below 300°K. Whereas AS in each case is due to a reduction in the thermal component of stress, the basic cause of the reduction is different for the interstitial and substitutional alloys. This is hinted at by the differences in concentration and temperature dependence of AS in each alloy system. AS in FeN during yielding and flow is attributed to an increase in mobile dislocation density, as compared with that of hydrogen-purified iron, arising from the mechanism of interstitial-impurity-induced cross-slip. AS in FeNi is attributed to a systematic reduction in the Peierls stress of iron with increasing Ni. Whereas AS in FeN is primarily of elastic origin, AS in FeNi is primarily of electronic origin. © 1969.